A thin-film magnetic device comprises, on a substrate, a composite assembly deposited by cathode sputtering and consists of a first layer made of a ferromagnetic material with a high rate of spin polarization, the magnetization of which is in plane in the absence of any electric or magnetic interaction, a second layer made of a magnetic material with high perpendicular anisotropy, the magnetization of which is outside the plane of said layer in the absence of any electric or magnetic interaction, and coupling of which with said first layer induces a decrease in the effective demagnetizing field of the entire device, a third layer that is in contact with the first layer via its interface opposite to that which is common to the second layer and made of a material that is not magnetic and not polarizing for electrons passing through the device.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A thin-film magnetic device comprising a substrate, a composite assembly deposited by cathode sputtering comprising: a first magnetic layer made of a material with a positive effective anisotropy, the magnetization of which is oriented perpendicular to the plane of said layer and the positive effective anisotropy per unit of surface area k2 including bulk and interfacial contributions is [(k v2 −2πM 2 2 )e 2 +k s2 ] where: k v is a volume anisotropy of the first magnetic layer; M is the magnetization of the first magnetic layer; e 2 is the thickness of the first magnetic layer; and k s2 is the interfacial anisotropy of the first magnetic layer; a second magnetic layer made of a material with a negative effective anisotropy, the negative effective k3 anisotropy per unit of surface area k3 including bulk density and interfacial contributions is [(k v3 −2πM 2 3 )e 3 +k s3 ] where: k v3 is a volume anisotropy of the second magnetic layer; M is the magnetization of the second magnetic layer; e 3 is the thickness of the second magnetic layer; and k s3 is the interfacial anisotropy of the second magnetic layer; said second magnetic layer having a spin polarization of at least 50%, wherein the second magnetic layer spin polarizes electrons traversing through the second magnetic layer when an electrical current flows perpendicular to the plane of the second magnetic layer; and a third non-magnetic layer, in direct contact with the second magnetic layer on its interface opposite to the interface with the first magnetic layer and made of a material that is not depolarizing for electrons passing through the third non-magnetic layer, wherein a coupling energy per unit of surface area between the first magnetic layer and the second magnetic layer is at least twice the absolute value of the effective negative anisotropy per unit of surface area of the second magnetic layer, and the sum of the effective magnetic anisotropy values k2+k3 is positive, and wherein the first magnetic layer is anchored and said device comprises means of causing an electric current to flow through its layers in a direction substantially perpendicular to the plane of said layers.
2. A thin-film magnetic device according to claim 1 , wherein the layer made of a material with the positive effective anisotropy comprises a material, an alloy or a multilayer of materials selected from the group consisting of cobalt, platinum, iron, nickel, palladium, gold and copper.
3. A thin-film magnetic device according to claim 1 , wherein the magnetic layer made of a ferromagnetic material with the spin polarization of at least 50% comprises a magnetic material selected from the group consisting of cobalt, iron, nickel or binary or ternary alloys thereof.
4. A thin-film magnetic device according to claim 1 , wherein the magnetic material that constitutes the layer of a ferromagnetic material with the spin polarization of at least 50% is crystallized or amorphous and contains added non-magnetic materials selected from the group consisting of boron, silicon, phosphorus, carbon, zirconium, hafnium or alloys thereof.
5. A thin-film magnetic device according to claim 1 , wherein the layer of a ferromagnetic material with the spin polarization of at least 50% comprising a multilayer of the magnetic metal/magnetic metal or magnetic metal/non-magnetic metal type.
6. A thin-film magnetic device according to claim 1 , wherein the third non-magnetic layer is made of a non-magnetic metal or a non magnetic oxide.
7. A thin-film magnetic device according to claim 1 , wherein a buffer layer is interposed between the substrate and the composite assembly made of the three layers.
8. A thin-film magnetic device according to claim 7 , wherein the buffer layer is made of one or more materials selected from the group consisting of platinum, tantalum, chromium, titanium, titanium nitride, copper, gold, palladium, silver or alloys thereof.
9. A thin-film magnetic device according to claim 7 , wherein the buffer layer comprises a plurality of layers.
10. A thin-film magnetic device according to claim 1 , wherein the substrate is made of a material selected from the group consisting of silicon, silica, silicon nitride, magnesium oxide, alumina and glass.
11. A magnetic tunnel junction with planar magnetization further comprising two active magnetic layers and the magnetic device according to claim 1 .
12. A magnetic tunnel junction with planar magnetization comprising two active magnetic layers, wherein at least one of the two active magnetic layers comprises the magnetic device according to claim 1 .
13. A magnetic tunnel junction with perpendicular magnetization comprising two active magnetic layers, wherein at least one of the two active magnetic layers comprises the magnetic device according to claim 1 .
14. A spin valve with planar magnetization further comprising two active magnetic layers and the magnetic device according to claim 1 .
15. A spin valve with planar magnetization comprising two active magnetic layers, wherein at least one of its two active magnetic layers comprises the magnetic device according to claim 1 .
16. A spin valve with perpendicular magnetization comprising two active magnetic layers, wherein at least one of its two active magnetic layers comprises the magnetic device according to claim 1 .
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
August 3, 2007
October 12, 2010
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